Finesse of transparent tissue cutting by ultrafast lasers at various wavelengths

Wang, Jenny; Schuele, Georg; Palanker, Daniel

doi:10.1117/1.jbo.20.12.125004

Cited by 16 publications

(8 citation statements)

References 37 publications

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“…The threshold energy required to generate seed electrons for LIOB formation exclusively via multiphoton absorption is approximately 10 13 W/cm 2 and cannot be safely induced in human skin [26,27]. The thermal initiation pathway assisted by chromophores results in a lower irradiance threshold, which lowers the irradiance threshold by 20 times [27], whereas ubiquitous water lowers the irradiance threshold by 10-100 times [27,28]. Therefore, transparent and weakly absorbing tissues such as the cornea mainly rely on the multiphoton-initiated optical breakdown, whereas highly absorbing tissues such as dark skin require a much lower energy threshold [24,29].…”

Section: Discussionmentioning

confidence: 99%

Photoaging and Sequential Function Reversal with Cellular-Resolution Optical Coherence Tomography in a Nude Mice Model

Wang

Chang

et al. 2022

IJMS

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Although nude mice are an ideal photoaging research model, skin biopsies result in inflammation and are rarely performed at baseline. Meanwhile, studies on antiphotoaging antioxidants or rejuvenation techniques often neglect the spontaneous reversal capacity. Full-field optical coherence tomography (FFOCT) can acquire cellular details noninvasively. This study aimed to establish a photoaging and sequential function reversal nude mice model assisted by an in vivo cellular resolution FFOCT system. We investigated whether a picosecond alexandrite laser (PAL) with a diffractive lens array (DLA) accelerated the reversal. In the sequential noninvasive assessment using FFOCT, a spectrophotometer, and DermaLab Combo®, the photodamage percentage recovery plot demonstrated the spontaneous recovery capacity of the affected skin by UVB-induced transepidermal water loss and UVA-induced epidermis thickening. A PAL with DLA not only accelerated skin barrier regeneration with epidermal polarity, but also increased dermal neocollagenesis, whereas the nonlasered group still had >60% collagen intensity loss and 40% erythema from photodamage. Our study demonstrated that FFOCT images accurately resemble the living tissue. The photoaging and sequential function reversal model provides a reference to assess the spontaneous recovery capacity of nude mice from photodamage. This model can be utilized to evaluate the sequential noninvasive photodamage and reversal effects after other interventions.

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Section: Discussionmentioning

confidence: 99%

Photoaging and Sequential Function Reversal with Cellular-Resolution Optical Coherence Tomography in a Nude Mice Model

Wang

Chang

et al. 2022

IJMS

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“…For example, the threshold energy for bubble formation in mouse intestine by 355-nm 500-ps pulses focused at NA = 1.2 amounts to only one third of the respective value in water (33 nJ vs 103 nJ) [130]. Threshold measurements with IR and UV fs laser pulses in water with increasing concentration of bovine serum albumin showed that at a concentration of 10mg/ml, the bubble threshold decreased by 40% for 400 nm pulses, compared to only 7% at 800 nm [57,131].…”

Section: Inter-band Energy States and Breakdown Initiationmentioning

confidence: 94%

“…To date, surgery has mostly been performed at 800 nm and 1040 nm, the wavelengths of Titanium:Sapphire lasers and ytterbium-based lasers [6,8,54]. Recently UV-A pulses have been employed for flap cutting in corneal refractive surgery because the shorter wavelengths provides a better cutting precision due to the shorter plasma length [55][56][57][58]134] Furthermore, the collagen molecules in corneal tissue act as stable centers of reduced excitation energy in UV breakdown that lower the breakdown threshold and minimize mechanical side effects [58]. On the other hand, the wavelengths considerably longer than 1040 nm have been tested for plasma-mediated surgery in strongly scattering tissues such as sclera, skin and brain [59][60][61]63] and in edematous corneas [64].…”

Section: Consequences For Femtosecond Laser Tissue Surgerymentioning

confidence: 99%

Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

et al. 2016

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The wavelength dependence of the threshold for femtosecond optical breakdown in water provides information on the interplay of multiphoton, tunneling and avalanche ionization, and is of interest for parameter selection in laser surgery. We measured the bubble threshold from UV to near-IR wavelengths and found a continuous decrease of the irradiance threshold with increasing wavelength λ. Results are compared to the predictions of a numerical model that assumes a bandgap of 9.5 eV and considers the existence of a separate initiation channel via excitation of valence band electrons into a solvated state followed by rapid upconversion into the conduction band. Fits to experimental data yield an electron collision time of ≈ 1 fs, and an estimate for the capacity of the initiation channel. Using that collision time, the breakdown dynamics was explored up to λ = 2 µm. The irradiance threshold first continues to decrease but levels out for wavelengths longer than 1.3 µm. This opens promising perspectives for laser surgery at wavelengths around 1.3 µm and 1.7 µm, which are attractive because of their large penetration depth into scattering tissues.

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“…The laser wavelength was fixed around 780 nm, but because the shock wave is highly non-linear, small variations in the laser wavelength should not play a significant role 29 . A wavelength between 700–1100 nm was used since water and most biological tissues are transparent in that region 20 .…”

Section: Resultsmentioning

confidence: 99%

Variability in bacterial flagella re-growth patterns after breakage

Paradis

Chevance

Liou

et al. 2017

Sci Rep

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Many bacteria swim through liquids or crawl on surfaces by rotating long appendages called flagella. Flagellar filaments are assembled from thousands of subunits that are exported through a narrow secretion channel and polymerize beneath a capping scaffold at the tip of the growing filament. The assembly of a flagellum uses a significant proportion of the biosynthetic capacities of the cell with each filament constituting ~1% of the total cell protein. Here, we addressed a significant question whether a flagellar filament can form a new cap and resume growth after breakage. Re-growth of broken filaments was visualized using sequential 3-color fluorescent labeling of filaments after mechanical shearing. Differential electron microscopy revealed the formation of new cap structures on broken filaments that re-grew. Flagellar filaments are therefore able to re-grow if broken by mechanical shearing forces, which are expected to occur frequently in nature. In contrast, no re-growth was observed on filaments that had been broken using ultrashort laser pulses, a technique allowing for very local damage to individual filaments. We thus conclude that assembly of a new cap at the tip of a broken filament depends on how the filament was broken.

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Finesse of transparent tissue cutting by ultrafast lasers at various wavelengths

Cited by 16 publications

References 37 publications

Photoaging and Sequential Function Reversal with Cellular-Resolution Optical Coherence Tomography in a Nude Mice Model

Photoaging and Sequential Function Reversal with Cellular-Resolution Optical Coherence Tomography in a Nude Mice Model

Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

Variability in bacterial flagella re-growth patterns after breakage

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